Speed up DB Discovery

[RPDben]

Hi,

I have a device in the central role that connects to a device with a specific name. I then do a db_discovery_start to get the handles of two of the characteristics. However, it takes a while for the BLE_DB_DISCOVERY_COMPLETE to be triggered (approx 750 - 1000ms). Is there anyway I can speed this up, or get rid of db_discovery altogether? Some additional points:

• I know the UUID of the characteristics
• I know the properties of the characteristic
• I will only ever connect to a device with these characteristics (if I do connect to a device without these characteristics I am happy for an error to be thrown and a reset triggered)

I am using:

• nRF52832
• S132 v4.0.2
• SDK13

My current ble_db_discovery_evt_handler() code is below:

static void ble_db_discovery_evt_handler(ble_db_discovery_evt_t *p_evt)
{
	ble_gatt_db_char_t * p_chars = p_evt->params.discovered_db.charateristics;
	uint8_t second_handle;
	if(p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE)
	{
		if(p_evt->params.discovered_db.srv_uuid.uuid == BLE_UNIQUE_SERVICE_UUID)
		{
			NRF_LOG_INFO("Found Service \r\n");
			for (uint32_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
			{
				switch(p_chars[i].characteristic.uuid.uuid)
				{
					case FIRST_CHARACTERISTC_UUID:
						first_handle = p_chars[i].characteristic.handle_value;
					break;
					case SECOND_CHARACTERISTC_UUID:
						second_handle = p_chars[i].characteristic.handle_value;
					break;
					default:
					break;
						
				}
			}
			sd_ble_gattc_read(p_evt->conn_handle, second_handle, 0);
		}
	}
	else
	{
		ble_db_discovery_start(&m_ble_db_discovery[p_evt->conn_handle], p_evt->conn_handle);
		NRF_LOG_WARNING("No DB Discovered: %d \r\n", p_evt->evt_type);
	}
}

Thanks in advance,

[run_ar]

If you control the device on the other side, and you make sure the attribute table doesn't change. You can use the handles directly without doing service discovery. Other than that I assume you are starting the discovery after receiving the connected event. So as soon as possible. Would be possible to speed things up uf you use a faster connection interval.

[RPDben]

Hi run,

I think I will have to use the handles directly. I do control all of the devices but it feels slightly wrong hard-coding the handle. I have the connection interval as fast as it can be and it is discovering as soon as it receives the connected event.

[run_ar]

I guess the main problem with hardcoding the handles would be if you do DFU and the attribute table change. e.g. you change SD version like in this case.

[RPDben]

Thanks, I will hard code the handles and ensure that there are no updates for the time being.

[run_ar]

Guess I should add a comment and point out that if you are bond to the peer you, can use service changed indications to get an indication if the attribute table change.